Really? That's pretty weird.
I've tried verifying the game cache, thinking that I may have deleted or altered a file when I was cleaning mods via BOSS. but even then it didn't work. It just crashes to desktop, no "Skyrim.exe has stopped working" window or anything.
Just today I tried a different tactic: using console commands, I gave myself Conjuration Duel Casting, as well as some extra magicka. I cast two Bound Dagger spells at the same time, and while the animation played through without any crashing, I only had the Bound Dagger in my left hand and not my right. My right hand was empty, save a faint purple glow. Tapping the mouse button for the right hand only made the little glowing spell-ball appear, as if I hadn't cast the spell at all.
With that said, I've also used console commands to give myself all the other bound weapons: bound bow, bound battleaxe, and bound sword. Casting Bound Bow and Battleaxe in my character's right hand doesn't crash the game, but casting bound sword does. So whatever the problem is, it's affecting the 1-handed bound weapons and not the two-handed ones. With that said, I've also noticed that while casting Bound Dagger in the left hand doesn't crash the game, the animation is a little choppy- as soon as my character's wrist is flicked, a regular Daedric dagger just pops into view for about one frame before the actual bound dagger magically appears in my hand. The two-handed weapon spells play out as normal.
This is very frustrating. I'm gonna try and comb through TES5Edit to see if there's a conflict or an error or something that's effecting them. If I can't fix this, I'm probably just going to give up and just do a complete clean install... though I really, really don't want to do that.